java - 如何从一组类创建一个类的实例？

Question

我有一个相似类的列表，它们都是同一个抽象类的子类。我还有一个 boolean 数组，它们应该对应于应该使用哪个类。

例如，我有一堆类，按以下约定命名:

boolean[] classesOn = new boolean[4];
abstract class myClass {}

class myClass1 extends myClass { public void myClass1(float x, float y) ...}
class myClass2 extends myClass {}
class myClass3 extends myClass {}
class myClass4 extends myClass {}
...

这个想法是只使用在 classesOn 中具有相应 boolean 值的类。为此，我使用 for 循环遍历 classesOn 并检查哪些是 true。现在我有以下代码:

for (int i = 0; i < classesOn.length; i++) {
  if (classesOn[i]) {
    switch (i) {
      case 0: c = new myClass1(x, y); break;
      case 1: c = new myClass2(x, y); break;
...

现在这是非常低效的，当我添加 myClass 的新扩展时，我需要添加一个新的案例。我希望能够只说 if (classesOn[i]) { c = new "myClass"+ (i + 1) ();} 来创建该特定类的实例。

我该怎么做？

(顺便说一句，这些只是示例，每个类的实际实现差异很大)

我目前正在研究的用途实际上是在处理中，其中有多种颜色方案，每个颜色方案都在一个类中表示。但我很好奇如何在未来的所有类型的类(class)中做到这一点。

我现在正在处理的确切代码如下所示 - (但我对一般答案感兴趣)

abstract class Scheme {
  float red,blue,green,x,y;
  String description;
  public void mousespot(){
    this.x = mouseX;
    this.y = mouseY;
    return;
  }
  public float getRed(){
    return this.red;
  }
  public float getBlue(){
    return this.blue;
  }
  public float getGreen(){
    return this.green;
  }
  public String getDescription(){
    fill(255,255,255);
    textSize(32);
    return this.description;
  }
}
class Scheme1 extends Scheme {
  public Scheme1(float x, float y) {
    this.description = "Green-Yellow-GW-Turqouise";
    this.red = map(x, 0, width, 0, 255);
    this.blue = map(y, 0, height, 0, 255);
    this.green = 255 * (float) dist(width/2, height/2, x, y) / (x / y);
  }
}

class Scheme2 extends Scheme {
  public Scheme2(float x, float y) {
    this.description = "Red-Yellow-Peach-Magenta";
    this.green = map(x, 0, width, 0, 255);
    this.blue = map(y, 0, height, 0, 255);
    this.red = 255 * (float) dist(width/2, height/2, x, y) / (x / y);
  }
}

在 mouseDragged() 方法中:

for (i = 0; i < colorschemesOn.length;i++) {
      if (colorschemesOn[i]) {
        switch(i) {
          case 0: 
            public Scheme selectedScheme = new Scheme1(mouseX,mouseY);
            break;
          case 1: 
            public Scheme selectedScheme = new Scheme2(mouseX,mouseY);
            break;
          case 2:
            public Scheme selectedScheme = new Scheme3(mouseX,mouseY);
            break;
          case 3:
            public Scheme selectedScheme = new Scheme4(mouseX,mouseY);
            break;
          case 4:
            public Scheme selectedScheme = new Scheme5(mouseX,mouseY);
            break;
          case 5:
            public Scheme selectedScheme = new Scheme6(mouseX,mouseY);
            break;
          case 6:
            public Scheme selectedScheme = new Scheme7(mouseX,mouseY);
            break;
          case 7:
            public Scheme selectedScheme = new Scheme8(mouseX,mouseY);
            break;
          case 8:
            public Scheme selectedScheme = new Scheme9(mouseX,mouseY);
            break;
          case 9:
            public Scheme selectedScheme = new Scheme10(mouseX,mouseY);
            break;
          case 10:
            public Scheme selectedScheme = new Scheme11(mouseX,mouseY);
            break;
          case 11:
            public Scheme selectedScheme = new Scheme12(mouseX,mouseY);
            break;
          default:
            public Scheme selectedScheme = new Scheme1(mouseX,mouseY);
            break;
        }
    }
}

Answer 1

不要依赖命名约定，而是创建一个数组:

Class<? extends myClass>[] classes = new Class<? extends myClass>[] { 
    myClass1.class, myClass2.class, myClass3.class, myClass4.class
};
boolean[] classesOn = new boolean[classes.length];

然后你可以用反射实例化它们:

if (classesOn[i])  { myClass c = classes[i].getConstructor().newInstance(); }

如果你的构造函数接受参数:

myClass c;
if (i < classesOn.lenght && classesOn[i])  { 
    c = classes[i]
        .getConstructor(float.class, float.class)
        .newInstance(mouseX, mouseY); 
} else {
    c = new myClass1(mouseX, mouseY);
}